Cornea cannot receive oxygen from the blood supply like other tissue. When the eye is open, the cornea primarily receives oxygen from the atmosphere, via the tears. When the eye is closed (e.g., during sleep), the cornea receives oxygen mainly from oxygen diffusion from the capillary plexus of the upper palpebral aperture vasculature. If sufficient oxygen does not reach the cornea, corneal swelling occurs. Extended periods of oxygen deprivation cause the undesirable growth of blood vessels in the cornea.
Wearing of a soft contact lens inevitably reduces the oxygen supply to the cornea, because it can form an oxygen barrier that prevents oxygen from reaching the cornea. The oxygen transmissibility of the contact lens worn by a patient is of vital importance for the oxygen supply to the cornea either from the atmosphere in the open eye state or from the capillary plexus of the upper palpebral aperture vasculature. In recent years, soft silicone hydrogel contact lenses become more and more popular because of their high oxygen transmissibility and comfort. By having high oxygen transmissibility, a silicone hydrogel contact lens allows sufficient oxygen to permeate through the lens to the cornea and to have minimal adverse effects on corneal health.
Recently, it has been proposed that liquid crystal electro-optic elements can be incorporated in contact lenses to provide electro-active, dynamic optics for vision correction of one or more focal lengths. See, U.S. Pat. Nos. 6,851,805, 7,490,936 and 8,154,804. However, the presence of those electro-optic elements inevitably substantially or totally prevent oxygen from permeating through the contact lens with the electro-optic elements therein to the cornea and can have detrimental effects on corneal health.
Therefore, there is still a need for a contact lens which would not rely on passive oxygen diffusion/transmission. A proposed solution to this problem described in this patent is to enable the contact lens to actively generate an in vivo oxygen supply directly to the cornea.